1. Field of the Invention
The present invention relates, in general, to hollow cam shafts, and particularly to cam shafts capable of supplying lubricating oil to the cam portions and the journal portions of the shaft.
2. Description of the Relevant Art
Hollow pipe members have been used as cam shafts for internal combustion engines in order to decrease weight. However, because the through-hole of the hollow pipe member typically has a large volume, it takes a long time to fill the hole with lubricating oil upon starting the engine. Thus, use of this kind of conventional hollow cam shaft is likely to result in initial scuffing due to the shortage of the lubricating oil in the through-hole during starting.
In order to obviate this drawback of conventional hollow cam shafts, the present invention is intended to provide an improved hollow cam shaft which can prevent initial scuffing due to the shortage of lubricating oil during starting.